Silver nanocrystals by hyperbranched polyurethane-assisted p(3)

106H.W.Luetal./MaterialsChemistryandPhysics81(2003)

104–107

Fig.3.UV-VisabsorptionspectraofsilvernanoparticlesobtainedinthepresenceofHPafterdifferentirradiationtime.(a)0h;(b)4h;(c)24hand(d)36h.

Fig.4.UV-Visabsorptionspectraofsilvernanoparticlesobtainedintheabsence(a)andpresence(b)ofHPafter36hirradiationtime.

wavelengths(blueshift).ThiseffectmaybeexplainedbytheincreasingelectrondensityonthesilverparticlesduetoalterationoftheFermilevel[18].

Incontrast,theAgNO3solutionintheabsenceofHPwasirradiatedinthesameconditions(Fig.4),butnocolorationandabsorptionbandcharacteristicofsurfaceplasmonreso-nancewereobserved.ItwasconceivablethatHPplayedakeyroleinthephotochemicalreductionofAg+.ItmaybeduetothecoordinationbetweenHPandAg+,whichmaydecreasethepotentialofAg+/Ag(EAg+/Ag)andpromotethereductionofAg+.3.4.FT-IRspectra

Tofurthercon rmtheinteractionbetweenHPandAg+,theinfraredspectraweremeasured.AscouldbeseeninFig.5,theabsorptionC=Ostretchingpeakof

HP

at1719cm 1shiftedto1715cm 1aftertheadditionofAgNO3,indicatingthattherewascoordinationbetweenHPandAg+.4.Conclusion

ThisworkpresentedanHP-assistedphotochemicalmethodforproducingsilvernanoparticlesbymeansofUVirradiation.X-raydiffractionresultsshowedthatapureface-centeredcubicsilverphasewasobtainedintheas-preparednanoparticles.TEManalysisshowedthatsilvernanoparticleswerehomogeneouslydispersedinHPmatrix.IntheUV-Visabsorptionspectraoftheobtainednanopar-ticles,theabsorptionpeakduetothesurfaceplasmonreso-nanceofsilverparticleswasobservedatabout430nm.HPwasfoundtoplayakeyroleinthephotochemicalreductionofsilverionsandtheformationofnanosizedparticles.

Fig.5.FT-IRtransmittancespectraofpureHP(a)andAg+-dopedHP

(b).